Packaging machine and method

ABSTRACT

Food products supported on trays, of the clear or opaque variety, are fed, either manually or automatically, between plastic webs which constitute an overwrap for the tray and a product carried thereby. The plastic webs follow paths which intersect and they are joined along a transverse line by heated sealing and cutting mechanisms. Tray supported products, for convenience called units, are fed toward and past the juncture of the webs, while the webs are unwound from their respective parent rolls, enveloping the unit to be packaged therebetween. Thereafter the longitudinal edges of the webs adjacent the unit are heat sealed and cut while simultaneously therewith the webs are transversely joined along transversely spaced lines adjacent the trailing end of the unit resulting in a hermetically sealed unit and joining of the web ends to provide a juncture for a subsequent package.

United States Billett et al.

[54] PACKAGING MACNE AND IVETHOD [72] Inventors: Ronald J. Billett, Sunnyvale: Wilhelmus 11'. Holtkamp, Milpitas; Veikko K. Viitanen, San Jose, all of Calif.

[73] Assignee: FMC Corporation, San Jose, Calif.

[22] Filed: July 28, 1969 [21] Appl. No.: 845,361

3,420,034 1/1969 Saraisky et a]. ..53/373 X Primary Examiner-Theron E. Condon Assistant Examiner-Eugene F. Desmond Attorney-F. W. Anderson and C. E. Tripp [57] ABSTRACT Food products supported on trays, of the clear or opaque variety, are fed, either manually or automatically, between plastic webs which constitute an overwrap for the tray and a product carried thereby. The plastic webs follow paths which intersect and they are joined along a transverse line by heated sealing and cutting mechanisms. Tray supported products, for convenience called units, are fed toward and past the juncture of the webs, while the webs are unwound from their respective parent rolls, enveloping the unit to be packaged therebetween. Thereafter the longitudinal edges of the webs adjacent the unit are heat sealed and out while simultaneously therewith the webs are transversely joined along transversely spaced lines adjacent the trailing end of the unit resulting in a hermetically sealed unit and joining of the web ends to provide a juncture for a subsequent package.

8 Claims, 32 Drawing Figures PATENTEDMAYIIO I972 3, 665 673 sum 01 [1F 17 INVENTORS RONALD J. BILLETT WILHELMUS u. nou'xmw BY VEIKKO x. vnnnzn ATTORNEYS PATENTEU MAY 3 0 I972 sum 02 0F 17 PATENTEDMAY30 I972 33, 665 673 sum 03 0F 17 F'IB EI PATENTEDMAY 30 I972 saw on HF 17 SHEET PATENTEDMAY 30 I972 PATENTEDMAY 30 m2 SHEET 09 0F 17 CNN D an m1 mmN.

EH nW-HII-HI Nfl nH-H-hHl HM EH-m- PATENTEDMM 30 I972 SHEET PATENTED MAY 3 0 I972 SHEET l 0F 17 PATENTEDHAY 30 I972 SHEET 15 0F 17 PATENTEDMM 30 m2 sum 17 0F 17 nm u h-n-ml PACKAGING MACHINE AND METHOD SUMMARY OF THE INVENTION The present invention discloses a packaging machine incorporating two parent web rolls which are simultaneously and intermittently unwound. The unwound webs are firmly held along their longitudinal edges by polished anvils and confronting endless belts and chains which follow curvilinear paths through part of their orbit. When web of the stretch type is utilized the paths followed by the chains are oriented to gradually diverge so that progressive stretching of the film takes place along an imaginary line, which is approximately at the intersection of the curvilinear paths. The end of each web is joined by a heated bar thus in effect producing one continuous web.

When packaging tray loaded fresh meat, the tray is advanced to the welded juncture of the webs either manually or automatically. Means may be provided, such as a photo cell or equivalent detecting device, for initiating unwinding of the webs at a speed substantially equal to the speed at which the tray or unit is transported. Continued movement of the tray brings the leading edge in contact with the joined webs and, as the webs unwind, the unit to be packaged is located therebetween. This stage of the process may be characterized as enveloping the unit in a U-shaped or looped elongation of a flexible web.

After the tray is completely enveloped by the web, unwindin g of the webs is interrupted and the tray is momentarily held stationary to allow operation of sealing mechanisms which bring the overlying longitudinal margins of the web together and, while so held, heated cutting and sealing devices join the webs laterally inwardly of its margins to produce the longitudinal side seams. Simultaneously with production of the side seams a portion of the web adjacent the trailing edge of the package is sealed and centrally cut which completes overwrapping of the tray. The cut transverse seam made adjacent the trailing edge of the package leaves a sealed portion which again joins the two webs together in preparation for packaging a subsequent tray.

Since the sealing mechanism for producing the longitudinal side seals and the seal adjacent the trailing end of the package have, in any particular design, limitations as to package length and width, packages having a variety of length and width dimensions below the maximum, as dictated by the sealing mechanism, can be packaged at random. Accordingly, this provides the degree of versatility required in those packaging situations encountered in supermarkets.

In accordance with the present invention a unique web gripping arrangement is provided which relies upon the adhesion of the film to polished blocks or anvils carried by sprocket chains. It has been discovered that by properly treating the surface of the anvils, which have a highly polished surface, over which the web is disposed, clamping of the web edges either by belts or individual clamps may be unnecessary. It has also been found that the adhesion of the web to the treated surface of the anvils is sufficient to prevent slipping of the web as long as the web lies substantially in the plane of the anvil surfaces. As will be explained in greater detail hereinafter, the web will be retained by the anvils when a positive acute angle is defined by the anvil surface and web while a negative angle (one which contributes to peeling of the web from the anvil surface) will not retain the web on the anvils.

Further in accordance with this invention a web sealing mechanism is provided which is operated sequentially to grip the web adjacent the package margins, cut the web to cited relaxation thereof and seal the relaxed web while the web around the package is held under tension. It was found that attempts to seal the web in stretched condition resulted in poor seal quality and in certain cases the web failed to seal at some areas.

It is a further feature of this invention to provide cooperating pairs of sprocket chains and V-belts, or equivalent mechanical devices, for gripping the web edges in those instances where the web material does not adhere to the polished anvils. An example of such web is cellophane. In handling web of this nature the edges are clamped between flexi ble tension devices, such as chains or belts or combinations thereof, which are in firm engagement. The clamping force may be adjusted as desired to insure web retention in those instances where the web is laterally stretched.

BRIEF DESCRIPTION OF TI-[E DRAWINGS FIG. 1 is a perspective view of the packaging machine constructed in accordance with the principles of the present invention,

FIG. 2 is a front elevation, on an enlarged scale, of the packaging machine of the present invention,

FIG. 3 is a side elevation of FIG. 2,

FIG. 4 is a diagrammatic view showing the drive arrangement for feeding the webs and for feeding the package,

FIG. 5 is a fragmentary enlarged detail, as viewed in the direction of the arrows 5-5 of FIG. 3, of the web feed conveyor,

FIG. 6 is a transverse section taken along the line 6-6 of FIG. 5,

FIG. 7 is an enlarged plan view of the sealing mechanism,

FIG. 8 is a side elevation of the web sealing mechanism showing the top and bottom sealing heads in retracted position,

FIG. 9 is a horizontal section taken along line 9-9 of FIG. 8 showing the bottom sealing head,

FIG. 10 is an enlarged section, taken substantially along line 10-10 of FIG. 7, showing the retracted position of the top and bottom sealing heads prior to being actuated to seal a package,

FIGS. 11, 12 and 13 illustrate the progressive action of the sealing heads during sealing of a package and show, respectively, bringing the webs in firm contact, cutting the webs, and sealing them,

FIG. 14 is a fragmentary perspective, located in rotated planes, showing the construction of the upper and lower sealing heads at the juncture of the side seal and the trailing seal,

FIG. 15 is an enlarged section, taken along line l515 of FIG. 7, showing on an enlarged scale, the construction of the top and bottom sealing bars for producing the seals at the trailing edge of the package and for joining the top and bottom webs together,

FIG. 16 is a section, taken substantially along line 1616 of FIG. 7, of the upper and lower sealing heads,

FIG. 17 is similar to FIG. 16 but shows the upper and lower sealing heads in contact which is the position assumed during the sealing operation.

FIG. 18 is an enlarged section taken substantially along line 18-18 of FIG. 7 showing the manner in which the upper gripping bar is guided for rectilinear movement and the means for gripping the web during the sealing operation,

FIG. 19 shows the relationship of parts when the upper sealing head is in firm contact with the lower sealing head,

FIG. 20 is an enlarged plan of a package infeed mechanism,

FIGS. 21, 22, 23 and 24 illustrate the progressive action of the package infeed mechanism for feeding a package to the sealing station,

FIGS. 25, 26, 27 and 28 are diagrammatic enlarged perspectives illustrating the steps involved in packaging a product,

FIG. 29 is a schematic of the control circuit of the packaging machine,

FIG. 30 is a diagrammatic perspective of a modification which may be applied to the upper stretch frame when it is desired to effect longitudinal as well as lateral or transverse stretching of the web,

FIG. 30A is side view of the modification of FIG. 30 adapted to the lower stretch frame, and

FIG. 31 is a diagrammatic perspective of another modification, which can also be applied to each stretch frame, when it is desired to prevent lateral or transverse stretching of the web.

GENERAL ARRANGEMENT The general arrangement of the machine embodying the present invention is shown in perspective in FIG. 1 and it is identified by the general numeral 20. Broadly, the machine comprises a bottom stretch frame 22 having laterally spaced and interconnected diverging side frames 22a and 22b. The divergent orientation of frames 22a and 22b is best illustrated in FIG. 2. Supported above the bottom stretch frame 22 is an upper stretch frame 24 including side frame members 24a and 24b which are also oriented in diverging relationship. Each of the stretch frames rotatably support unwind shafts 26 and 28 rotatably mounted, respectively, on the lower stretch frame 22 and the upper stretch frame 24. A bottom web roll BWR of packaging web BW is mounted on the unwind shaft 26 while a top web roll TWR of packaging web TW is mounted on the unwind shaft 28. The top and bottom webs are unwound and transversely stretched by a web feed arrangement comprising V-belts 32 and 34 associated with the upper stretch frame 24 and cooperating sprocket chains 36 and 38 also associated with the upper stretch frame 24. As shown in FIG. 2 the lower stretch frame 22 also includes V-belts, identified as 40 and 42, and sprocket chains 44 and 46. Since the arrangement and cooperation of the V-belts and sprocket chains are identical in each stretch frame 22 and 24 the description herein will be confined to the upper stretch frame 24.

The longitudinal edges or margins of the web TW are received between the chains 36 and 38 and the V-belts 32 and 34, to, in part, initiate unwinding of the web from the web roll. Since the distance between the chains 36 and 38 progressively increases, the web TW is transversely stretched with the maximum lateral or transverse stretching occurring when the chains 36 and 38 start traversing the horizontal reach defined by sprockets 92 rotatably mounted on the upper stretch frame 24.

At the juncture of the lower stretch frame 22 and the upper stretch frame 24 a web sealing mechanism, indicated by the general numeral 50, is provided for producing longitudinal and transverse seals about the unit to be packaged. The sealing mechanism includes a lower sealing head 52 and an upper sealing head 54 (FIG. 8) which are reciprocated simultaneously toward and away from each other in response to the presence of a package between the webs. When the sealing heads 52 and 54 come in contact with each other, the top and bottom webs are joined along the line .I (FIG. 1) which is approximately in the plane containing the juncture of the bottom and top stretch frames 22 and 24. Items or units to be packaged are fed into the machine in the direction of the arrow A on an infeed table 56. The package is fed to make contact with the looped portion of the webs at the juncture J thus enveloping the package or item to be packaged between the webs BW and TW. The item to be packaged together with the sealed loop and of the webs is transported within the confines of the sealing mechanism 50. After the item has moved a sufficient distance to come within confines of the sealing mechanism 50 the upper and lower sealing heads 54 and 52, respectively, are reciprocated toward each other joining the top and bottom webs along lines inwardly adjacent the marginal edges thereof and along a transverse line adjacent the trailing edge of the package. The transverse seal is severed, when made, to form both the trailing end of the leading package and the leading end of the next package. Since the longitudinal seals are spaced laterally inwardly of the web edges astrip of waste material is produced. Such waste, which comprises a band of film S (FIG. 25), is wound up on spools 60 rotatably mounted on arms 62 carried by the upper stretch frame 24.

Referring to FIG. 1 it will be observed that the packaging apparatus is provided with drive means generally indicated by the numeral 64 which includes a motor 66 driving a chain and sprocket arrangement 68 which is connected to drive the web feed chains 36 and 38, of the upper stretch frame 24, and the chains 44 and 46, of the lower stretch frame 22. The drive is connected to a sprocket chain 70 mounted adjacent and on one of the longitudinal edges of the infeed table 56. The chain 70 is driven by a sprocket 72 and is trained about an idler sprocket 74. The idler sprocket 74 is mounted on a bracket 76 (FIG. 1.) secured to the infeed table 56. Attached to the chain 70 is a product pusher bar 78 which directs products to be packaged toward the web juncture .I. In moving the product toward the webs, resilient product centering shoes 80 are encountered which center the product before it is enveloped by the webs. Inspection of the FIG. 2 will reveal that the drive motor 66 is mounted on a plate 82 which is secured to the side frame members 22a and 22b at a slight angle with respect to the horizontal. Further and more detailed explanation of the drive for the packaging machine of the present invention will be given in connection with FIG. 4.

According to the above description of the general arrangement of the packaging machine of the present invention it should be appreciated that it provides automatic packaging of articles of random size and shape between two hermetically sealed webs which minimizes, particularly those packages having certain dimensions of length and width, the amount of film required to produce a marketable package. Further the machine of the present invention provides a unique method of holding the margins of the film while it is being stretched and maintains the film of the package in the stretched condition until the package is hermetically sealed. After the package tray is enveloped and sealed between a pair of webs, and the stretching force is removed, the film assumes a tightly stretched condition over the packaged product.

WEB DRIVE As indicated previously the lower and upper stretch frames 22 and 24, respectively, are substantially identical in construction and such similarity in construction also relates to the frame structures and the manner in which the V-belts 32, 34, 40 and 42 and the chains 36, 38, 44 and 46 are related and driven. Accordingly this portion of the description will be confined to the upper stretch frame 24 while any differences that exist will be specifically pointed out. As shown in FIGS. 1, 2 and 3 the upper stretch frame 24 includes a plurality of interconnected structural members which support the various sprockets and pulleys for the chains 36 and 38 and the V belts 32 and 34. Each of the side frames 24a and 24b of the upper stretch frame 24 takes the general form of a truncated right triangle including a vertically extending member 84 secured at its upper end to a horizontal member 86 and a member 88 extending at an acute angle relative to the member 84. As shown on FIG. 3, arcuate chain guiding tracks 90, for guiding the chains 36 and 38, are secured to the members 88. Reference to FIG. 2 will reveal that the tracks 90 assume the divergent orientation of the side frame members 24a and 24b.

Each of the chains 36 and 38 carries a series of closely adjacent anvil or web gripping blocks spaced in close proximity along the entire length of the chains 36 and 38. As shown in FIGS. 5 and 6 the blocks are provided with a V groove 102 and a highly polished smooth surface 104 (herein shown as a flat surface although surfaces of other configurations may be utilized) against which a web adheres. While the particular technical reasons for firm adherence of the web to the polished surface 104 of the anvil blocks 100 do not appear to be completely understood, in practice it has been found that the adherence of PVC web is sufficient to effect stretching thereof without significant contribution by the V belts 32 and 34. As the belts 32, 34 leave the sprockets 94, they pass up over pulleys 105 and on to sprockets 96 (FIGS. I and 3).

The construction lines R and T in FIG. 6 represent, respectively, the plane containing the surface 104 of the anvils 100 and the plane containing the web TW in the vicinity of the an- 

1. A packaging apparatus having a frame structure mounting two rolls of stretchable heat sealable thermoplastic web, said apparatus comprising means engageable with the longitudinal margins of the webs for simultaneously unwinding and traversely stretching each web, said webs following paths merging toward a common plane, sealing means movable in a direction substantially normal to said plane for joining the ends of each web along a transverse line to thereby produce a continuous web, means for feeding products to be packaged toward and against the intersection of said webs and concurrently feeding the webs so that the product being packaged is located in a loop formed by the webs, and means for sealing the loop adjacent the sides and trailing end of the product while simultaneously therewith joining the web by said first mentioned sealing means to produce a continuous web.
 2. The packaging apparatus according to claim 1 wherein said means for sealing the web at the sides and trailing end of the product includes web clamping bars having their web engaging surfaces treated so that the web firmly adheres thereto.
 3. The apparatus according to claim 1 wherein said web unwinding means comprises frame structures, each frame structure mounting web unwinding and feeding conveyors, means on each of said conveyors for firmly holding the edges of the web, said frame structures being oriented to cause lateral stretching of the web as it is unwound.
 4. A method of packaging products in heat sealable thermoplastic film comprising the steps of transversely stretching the film, forming a loop in the film while it is in its stretched condition, inserting an item to be packaged in the loop, and heat sealing the overlying loop portions of the web to produce an overwrapped product, wherein said heat sealing of the loop portions comprises the steps of clamping the overlying web portions together adjacent the edges of the product to relax the tension occasioned by stretching, and sealing and cutting the relaxed portions of the web.
 5. Film packaging apparatus comprising laterally spaced, loops of endless web gripping members, means for feeding a web of film into a gripping reach of said members, means for moving said gripping members along for advancing the gripped web, means mounting said gripping members for diverging movement in the direction of web advance along said gripping reach for stretching the web transversely as it is advanced, means for wrapping the articles in the web downstream of said gripping members, and web gathering means upstream of said web gripping reach for drawing the web edges together before they are gripped by said endless members.
 6. In a packaging machine of the type which applies a stretch thermoplastic web around a product to be packaged and heat seal the web to enclose the product in the web, the improvement in heat sealing the web comprising means, engageable with the longitudinal edges of overlying tranversely spaced web portions, for holding and maintaining said web portions in tension while a product is disposed therebetween; means for clamping the spaced web portions adjacent the margins of the product to be packaged and inwardly of said holding and maintaining means; said clamping means being effective to further stretch the web portions increasing the tension of the web about the product before the spaced web portions are clamped; and means for cutting the clamped webs adjacent the line along which they are clamped to relax the web edges and then heat sealing the web edges.
 7. A packaging apparatus having a frame structure mounting two rolls of stretchable heat sealable thermoplastic webs, said apparatus comprising means engageable with the longitudinal margins of the webs for simultaneously unwinding and transversely stretching each web, said webs following paths merging toward a common plane, sealing means movable in a direction substantially normal to said plane for joining the ends of each web along a transverse line to thereby produce a continuous web, means for feeding products to the packaged toward and against the intersection of said webs and concurrently feeding the webs so that the product being packaged is located in a loop formed by the webs, and means for sealing the loop adjacent the sides and trailing end of the product while simultaneously therewith joining the webs by said first mentioned sealing means to produce a continuous web, said web unwinding means comprises anvil blocks having polished surfaces to which the webs firmly adhere.
 8. A packaging apparatus having a frame structure mounting two rolls of stretchable heat sealable thermoplastic web, said apparatus comprising means engageable with the longitudinal margins of the webs for simultaneously unwinding and transversely stretching each web, said webs following paths merging toward a common plane, sealing means movable in a direction substantially normal to said plane for joining the ends of each web along a transverse line to thereby produce a continuous web, means for feeding products to be packaged toward and against the intersection of said webs and concurrently feeding the webs so that the product being packaged is located in a loop formed by the webs, and means for sealing the loop adjacent the sides and trailing end of the product while simultaneously therewith joining the webs by said first mentioned sealing means to produce a continuous web, said web unwinding means including anvil blocks having polished surfaces to which each web firmly adheres, and sprocket chains mounting said anvil blocks, said chains travelling in orbits that cause lateral stretching of the webs as the webs are advanced to the product feeding means. 